Normal lens cell behavior is characterized by regulated cell division and specialized gene expression. However, loss of such regulation is sometimes associated with aging and the premature malfunctioning of the lens. Our program has utilized methods to explore the physiological state of the lens epithelium. By studying the effects of varied cytoplasmic environments on the lens cell nucleus through the technique of nuclear transplantation, the capability of the nucleus to take part in cell division and gene action are understood. These experiments are being continued in order to demonstrate the regulation of function of the lens epithelium in different conditions: the embryo, the adult, after wounding, and in vitro culture. In addition to nuclear transplantation, histological techniques, autoradiography, as well as microscopic analysis of living cells, are performed. The current proposal describes an investigation of the in vitro cultured state of the lens, which aims at elucidating the regulation of cell division in the lens epithelium and the interaction of the epithelial cells with the lens fibers and capsule. Assay of DNA synthesis and mitosis will be correlated with examination of the specific crystallin protein content of the cells by immunofluorescence. These varied approaches will elucidate the factors regulating lens function and the disturbances associated with the human subcapsular cataract and the aging of lens cells.